Tighten up outlines and fieldsets

Objective:

* Make outline widgets and fieldset layouts take up a little less space

Bonus:

* Fix option icons always showing up on the first item because the option
  wasn't position relative

Changes:

ve.ui.Widget.css
* Add position: relative to option widgets
* Cleanup unused background properties for outline items
* Reduce padding for outline items
* Move icons to match padding changes

ve.ui.Layout.css
* Reduce margins for fieldset layouts, including using a negative top
  margin to compensate for the overly tall legend

Change-Id: Ida6147b8171dcb4152ca9be0e099a5f9b81ac1c0
Merge "Tighten up outlines and fieldsets"